The present invention relates to a device for testing seals, and more specifically to a vacuum test tool to detect leaks in sealed gaps.
Often structures that are subject to internal or external pressurization have areas susceptible to defects that result in unacceptable pressure disturbances. For example, the gaps around aircraft doors, windows, hatches, or other inserts must be completely sealed to maintain adequate pressurization of the passenger cabin. Early detection of a pressure leak during the manufacture or maintenance of a structure is desired to avoid downstream corrections that generally require additional time, expense, and labor. It is also desirable to routinely and easily test for leaks during scheduled maintenance.
Seals around aircraft doors and hatches have typically been installed early in the production cycle. However, the adequacy of the seal could be first tested only during a "full blow" test wherein the entire fuselage is pressurized to in-flight conditions. "Full blow" occurred only after the fuselage was capable of being pressurized; typically very late in the production cycle after doors, windows, hatches and their respective seals and decorative trim had all been installed. Therefore, discovery of defective seals or seams during "full blow" required substantial rework to dismantle portions of the aircraft to fix or replace the defective seal.
Vacuum force has been used to detect air leaks in a section of a seam as demonstrated in U.S. Pat. Nos. 2,108,176, 2,660,053, and 4,002,055. These patents teach detection of leaks by placing a windowed vacuum chamber over part of a seam that has been coated with a soapy film. Application of a vacuum force draws air through leaks in the seam, thereby forming soap bubbles along the leaking area. This leak detection method is labor intensive not practical for testing seals in areas where soap bubbles are difficult to see, such as along seals recessed in gaps around aircraft doors, windows, hatches, etc.
These patents also teach the use of a fairly small vacuum chamber with a narrow perimeter seal to maintain suction. The resulting load on the structure surrounding the seam is concentrated along the narrow perimeter area. Applying the same vacuum chamber concept to larger area, such as around a door, window, hatch, etc., puts a substantial load on the surrounding structure. These large pressure loads may result in damage to the surrounding structure and thus unacceptable. Accordingly, for leak testing large cut-out areas it is desired to spread vacuum loads over the entire surface to prevent excess loading on the aircraft structure under the test equipment.
It is therefore a principal object of the present invention to provide a testing apparatus that allows a user to quickly, efficiently and reliably test a seal or seam in for unwanted leaks without potential damage to the structure being tested. It is also an important goal to do such leak testing early in the production cycle while any leakage is relatively easy to repair.